Low-to-high voltage current coupler circuit

ABSTRACT

A circuit is provided which can apply a current which exists at a low voltage to the input terminal of apparatus, such as a cathode-ray tube, which must be biased at a high voltage.

United States Patent Inventor Ted W. Berwin Los Angeles, Calif. Appl.No. 868,664 Filed Oct. 6, 1969 Patented Sept. 28, 1971 Assignee HughesAircraft Company Culver City, Calif.

LOW-TO-HIGH VOLTAGE CURRENT COUPLER CIRCUIT 9 Claims, 1 Drawing Fig.

501 FieldofSearch 328/226, 2523;315/170, 172, 173; 320/1; 307/49, 77,85, 296; 321/15 [56] References Cited UNITED STATES PATENTS 2,797,3025/1957 Smith 320/1x 3,199,014 8/1965 Putzrath 320/1 PrimaryExaminerWilliam H. Beha, Jr. Auorneys-james K. Haskell and Walter 1.Adam ABSTRACT: A circuit is provided which can apply a current whichexists at a low voltage to the input terminal of apparatus, such as acathode-ray'tube, which must be biased at a high voltage.

PATENTEU SEP28IE17I duzzawr fawez Anna 5y LDW 'll'D-Hllfillli VOLTAGECURRENT CDllJlPLlElR CllHtClJllll BACKGROUND OF THE lNVENTlON Thisinvention relates to current-coupling circuits and more particularly toimprovements therein.

In the suppressed cathode operation of storage tubes, DC control fromgrid to cathode is required. When the cathode is biased at a voltagefrom one to six lrilovolts, a special coupler circuit is required to beused. Voltage couplers do exist for this purpose. These are pulse widthcouplers for example. Current couplers, as far as is known, do not existand in order to apply a current to the cathode of the storage tube itwas necessary to convert the current to a voltage.

OBJECTS AND SUMMARY OF THE llNVENTlON An object of this invention is toprovide a coupler circuit which can couple currents existing at arelatively low voltage level (near volts) to the terminals of apparatuswhich exist at a relatively high voltage level.

Another object of this invention is to provide a current coupler whichcan couple current existing at substantially ground voltage level to thecathode of a cathode-ray tube biased at a high voltage level.

Yet, another object of the present invention is the provision of a noveland useful current coupling circuit.

These and other objects of the invention are achieved in an arrangementwherein two capacitors are provided with arrangements to connect one tothebiasing source of the storage tube to be charged therefrom while theother, which has previously charged, is in a path which couples thecurrent source at ground level to the cathode of the storage tube, andmeans are provided for switching the described connections of thecapacitors.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will best be understood from thefollowing description when read in conjunction with the accompanyingdrawings.

ElltlElF DESCRllPTlON OF THE DRAWING The drawing is a circuit diagram ofan embodiment of the invention.

DESClRlPTllON OF THE PREFERRED EMBODIMENT In the circuit diagram of theinvention shown in the drawing, it is desired to apply current from acurrent source 10, which exists at a voltage level near ground, to thecathode 12 of a storage tube 114, wherein a bias from a bias source 16is applied between the cathode l2 and the control grid 18. Current fromthe source is applied through a resistor 20 to the emitter of atransistor 22. A bias is also applied to this emitter through resistor24 and a potentiometer 26 which is connected to a negative biasingsource.

The base of transistor 22 is connected to a known thermalcompensatingarrangement which includes a transistor 28 whose base is coupled to thebase of transistor 22 and also to its collector. its collector isconnected through a resistor 30 to a positive potential source. ltsemitter is connected to ground.

The collector of transistor 22 is connected to the emitters of twotransistors respectively 32 and 34. Transistor 32 has its collectorconnected to the cathode of a diode 36 and to one side of a capacitor38. The other side of the capacitor 38 is connected to the anode of thediode 40, and to emitter of a transistor 432. The collector oftransistor 42 is connected to the cathode E2 of the storage tube M. Thebase of transistor 42 is connected to the grid 18 of the storage tube M.

The transistor 34 has its collector connected to the cathode of a diodedd and to one side of a capacitor 46. The other side of the capacitor416 is connected to the anode of the diode 48 and to the emitter of atransistor 50. The collector of transistor 50 is connected to thecathode 12 of the storage tube 14. The base of the transistor 50 is alsoconnected to the control grid 18 of the storage tube.

The cathodes of diodes W and 48 are connected to the bases oftransistors 42 and 5d The anode of diode 36 is connected to one end of aresistor 52, to the cathode of a diode 54, and to the collector of atransistor 56. The anode of diode 44 is connected to one end of aresistor 58, to the cathode of a diode 60, and to the collector of atransistor 62. Resistors 52 and 58 are connected to a positive potentialsource (on the order of +50 volts) The anodes of diodes 54 and 60 areconnected to a positive potential source (on the order of +12 volts).The emitters of transistors 5s and 62 are connected to the crossconnected diodes respectively 64 and 66. The emitters of transistors 56and 62 are also respectively connected through resistors 68 and 70, toa. negative potential source, (on the order of l2 volts).

The base of transistor 62 and the base of transistor 34 are respectivelyconnected to a positive potential source, (on the order of 6 volts). Anoscillator 72, which by way of illustration, in an embodiment of theinvention, was a free running oscillator having a frequency on the orderof 20 kHz. This oscillator has its output applied to the bases oftransistors 32 and 56 for the purpose of gating them on and off at the20 kHz. rate.

The operation of the system is as follows:

When the oscillator 72 biases transistors 32 and 56 so that they areconductive, by virtue of the cross coupling, transistors 34 and 62 arerendered nonconductive. Diode 36 is back-biased and therefore isblocked. Capacitor 46 can be charged from the potential source 16through a path which includes diode 48, capacitor 46, diode 44, resistor58 and the positive potential source to which it is connected. Currentflows from the current source 10 through transistor 22,

'through transistor 32, through capacitor 38, and through transistor 42into the cathode 12.

When transistors 32 and 56 are cut off, then transistors 34 and 62 arerendered conductive. A path is provided for the current source throughtransistor 22, through transistor 34, through capacitor 46, and throughtransistor 50 to the cathode 12. Meanwhile, capacitor 38 is beingcharged up from the bias source to through the path provided by thediode 40, capacitor 38, diode 36 and resistor 52 to the positivepotential source.

From the foregoing it will be seen that when capacitor 38 is beingcharged up from the bias potential which is applied to the control grid,capacitor 46 which has previously been charged up from that bias sourceis permitted to conduct current from the current source 10 to thecathode of the storage tube. Thereafter, capacitor 38 is switched intothe current conducting path between the current source and the cathodeof the storage tube while capacitor 46 is connected to be recharged fromthe bias source. In this manner the high potential difference betweenthe control grid and the cathode is maintained while current is appliedto the cathode from the current source which is at a low potentialvalue.

From the foregoing, there has been described and shown a novel, usefuland unique coupling circuit.

What is claimed is:

l. A circuit for coupling current from a source at a relatively lowvoltage level to apparatus biased at a relatively high voltage levelfrom a high voltage level source comprising:

a first and a second capacitor,

first switch means for coupling said first capacitor to said relativelyhigh voltage source for charging when activated,

second switch means for coupling, said current source to said apparatusthrough said first capacitor when activated, third switch means forcoupling said second capacitor to said high voltage source for chargingwhen activated,

fourth switch means for coupling said current source through said secondcapacitor to said apparatus when activated, and

means for alternatively activating said first and fourth switch meansfor coupling and then said second and third switch means for coupling.

2. Apparatus as recited in claim 1 wherein said means for alternativelyactuating said first and fourth switch means for coupling comprises anoscillator.

3. Apparatus as recited in claim 1 wherein said first means for couplingincludes first diode means coupled between said source of high voltageand one side of said first capacitor,

a second diode means coupled between the other side of said firstcapacitor and said source of high voltage, and

first transistor means for biasing said second diode means nonconductivewhen said first transistor means is rendered conductive.

4. Apparatus as recited in claim 3 wherein said second coupling meansincludes a second transistor means coupling said current source to saidother side of said first capacitor, and

a third transistor means coupling said one side of said capacitor to theinput of said apparatus.

5. Apparatus as recited in claim 1 wherein said third coupling meansincludes third diode means coupled between said source of high voltageand one side of said second capacitor means,

fourth diode means coupling said other side of said second capacitormeans to the source of high voltage, and

fourth transistor means for rendering said third diode meansnonconductive when said fourth transistor means is rendered conductive.

6. Apparatus as recited in claim 4 wherein said fourth means forcoupling includes fifth transistor means for coupling said currentsource to said other side of said second capacitor means, and

sixth transistor means for coupling said one side of said capacitormeans to said apparatus.

7. In a system where it is required to couple current from a sourcewhich is at a relatively low voltage value to the input terminal ofapparatus which must be maintained at a relatively high voltage value bya high voltage value bias source having first and second outputterminals,

a coupling circuit comprising a first capacitor means,

a second capacitor means,

first means for charging said first capacitor means from said highvoltage bias source,

second means for coupling said current source to said apparatus inputterminal through said second capacitor means while said first capacitormeans is being charged from said high voltage bias source,

third means for charging said second capacitor means from saidrelatively high voltage bias source,

fourth means for coupling said current source through said firstcapacitor means to said apparatus input terminal while said secondcapacitor means is being charged from said relatively high voltagesource,

first switching means for switching said first capacitor means from saidfirst means to said fourth means, and

second switching means for switching said second capacitor means fromsaid second means to said third means when said first switching meansswitches said first capacitor means from said first means to said fourthmeans.

8. Apparatus for coupling a current source at a relatively low potentiallevel to the input terminal of apparatus which is biased by a relativelyhigh voltage source having a first and second output terminal to apotential at a relatively high level,

said apparatus comprising a first capacitor means,

a second capacitor means,

means for coupling said first capacitor means to be charged by saidrelatively high voltage potential source including a first diode coupledbetween said relatively high voltage potential source and one side ofsaid first capacitor means,

a second diode coupled between the other side of said first capacitormeans and the other output terminal of said relatively high voltagesource, and

first transistor means for controlling the conductivity of said seconddiode means, means for coupling said second diode means to said highvolta ge source for chargingbcomprising: third diode means coupling t efirst output terminal of said high voltage source to one side of saidsecond capacitor means,

fourth diode means coupling the other side of said second capacitormeans to the second output terminal of said high voltage source, and

fourth diode means coupling the other side of said second capacitormeans to the second output terminal of said high voltage source, and

a second transistor means for controlling the conductivity of saidfourth diode means,

means for coupling said current source to said apparatus input terminalthrough said first capacitor means includmg:

third transistor means coupling said current source to said other sideof said first capacitor means, and

fourth transistor means coupling said one side of said first capacitormeans to the input terminal to said apparatus,

means for coupling said current source through said second capacitormeans to said apparatus input terminal comprising:

fifth transistor means coupling said current source to said other sideof said second diode means, and

sixth transistor means coupling said one side of said other capacitormeans to said terminal of said apparatus, and

oscillator means for alternately rendering said first and secondtransistor means conductive when said fourth and fifth transistor meansare nonconductive.

9. Apparatus as recited in claim 6 wherein said fourth and sixthtransistor means each has a collector, base and emitter electrode, andthere are included means connecting the collectors of said fourth andsixth transistors to the input terminal of said apparatus,

means connecting the bases of said fourth and sixth transistors to oneterminal of said high voltage source,

said first and third diodes each has an anode and a cathode,

means connecting said first diode means anode to said fourth transistoremitter,

means connecting said third diode anode to said sixth transistoremitter, and

means connecting the cathodes of said first and third diodes to thebases of said fourth and sixth transistors,

said first and second transistor means each has a base emitter andcollector electrode,

means connecting the collector of said first transistor to the anode ofsaid second diode,

means connecting said first transistor collector to the other terminalof said high voltage source,

means connecting said first transistor emitter to a source of biasingpotential,

diode means coupling the emitter of said first transistor to the emitterof said second transistor,

oscillator means coupled to the bases of said first and thirdtransistors for alternately rendering them conductive,

means connecting the collector of said second transistor to the anode ofsaid fourth diode,

means connecting said second transistor collector to the other terminalof said high voltage source,

said third and fifth transistor means each having a collector base andemitter electrode,

means connecting the collectors of said third and fifth transistor meansto the cathodes to the respective cathodes of said second and fourthdiodes,

means connecting the emitters of said third and fifth transistor meansto said current source,

means connecting the base of said third transistor means to the base ofsaid first transistor means and means connecting the base of said fifthtransistor means to the base of said second transistor means.

1. A circuit for coupling current from a source at a relatively lowvoltage level to apparatus biased at a relatively high voltage levelfrom a high voltage level source comprising: a first and a secondcapacitor, first switch means for coupling said first capacitor to saidrelatively high voltage source for charging when activated, secondswitch means for coupling, said current source to said apparatus throughsaid first capacitor when activated, third switch means for couplingsaid second capacitor to said high voltage source for charging whenactivated, fourth switch means for coupling said current source throughsaid second capacitor to said apparatus when activated, and means foralternatively activating said first and fourth switch means for couplingand then said second and third switch means for coupling.
 2. Apparatusas recited in claim 1 wherein said means for alternatively actuatingsaid first and fourth switch means for coupling comprises an oscillator.3. Apparatus as recited in claim 1 wherein said first means for couplingincludes first diode means coupled between said source of high voltageand one side of said first capacitor, a second diode means coupledbetween the other side of said first capacitor and said source of highvoltage, and first transistor means for biasing said second diode meansnonconductive when said first transistor means is rendered conductive.4. Apparatus as recited in claim 3 wherein said second coupling meansincludes a second transistor means coupling said current source to saidother side of said first capacitor, and a third transistor meanscoupling said one side of said capacitor to the input of said apparatus.5. Apparatus as recited in claim 1 wherein said third coupling meansincludes third diode means coupled between said source of high voltageand one side of said second capacitor means, fourth diode means couplingsaid other side of said second capacitor means to the source of highvoltage, and fourth transistor means for rendering said third diodemeans nonconductive when said fourth transistor means is renderedconductive.
 6. Apparatus as recited in claim 4 wherein said fourth meansfor coupling includes fifth transistor means for coupling said currentsource to said other side of said second capacitor means, and sixthtransistor means for coupling said one side of said capacitor means tosaid apparatus.
 7. In a system where it is required to couple currentfrom a source which is at a relatively low voltage value to the inputterminal of apparatus which must be maintained at a relatively highvoltage value by a high voltage value bias source having first andsecond output terminals, a coupling circuit comprising a first capacitormeans, a second capacitor means, first means for charging said firstcapacitor means from said high voltage bias source, second means forcoupling said current source to said apparatus input terminal throughsaid second capacitor means while said first capacitor means is beingcharged from said high voltage bias source, third means for chargingsaid second capacitor means from said relatively high voltage biassource, fourth means for coupling said current source through said firstcapacitor means to said apparatus input terminal while said secondcapacitor means is being charged from said relatively high voltagesource, first switching means for switching said first capacitor meansfrom said first means to said fourth means, and second switching meansfor switching said second capacitor means from said second means to saidthird means when said first switching means switches said firstcapacitor means from said first means to said fourth means.
 8. Apparatusfor coupling a current source at a relatively low potential level to theinput terminal of apparatus which is biased by a relatively high voltagesource having a first and second output terminal to a potential at arelatively high level, said apparatus comprising a first capacitormeans, a second capacitor means, means for coupling said first capacitormeans to be charged by said relatively high voltage potential sourceincluding a first diode coupled between said relativelY high voltagepotential source and one side of said first capacitor means, a seconddiode coupled between the other side of said first capacitor means andthe other output terminal of said relatively high voltage source, andfirst transistor means for controlling the conductivity of said seconddiode means, means for coupling said second diode means to said highvoltage source for charging comprising: third diode means coupling thefirst output terminal of said high voltage source to one side of saidsecond capacitor means, fourth diode means coupling the other side ofsaid second capacitor means to the second output terminal of said highvoltage source, and a second transistor means for controlling theconductivity of said fourth diode means, means for coupling said currentsource to said apparatus input terminal through said first capacitormeans including: third transistor means coupling said current source tosaid other side of said first capacitor means, and fourth transistormeans coupling said one side of said first capacitor means to the inputterminal to said apparatus, means for coupling said current sourcethrough said second capacitor means to said apparatus input terminalcomprising: fifth transistor means coupling said current source to saidother side of said second diode means, and sixth transistor meanscoupling said one side of said other capacitor means to said terminal ofsaid apparatus, and oscillator means for alternately rendering saidfirst and second transistor means conductive when said fourth and fifthtransistor means are nonconductive.
 9. Apparatus as recited in claim 6wherein said fourth and sixth transistor means each has a collector,base and emitter electrode, and there are included means connecting thecollectors of said fourth and sixth transistors to the input terminal ofsaid apparatus, means connecting the bases of said fourth and sixthtransistors to one terminal of said high voltage source, said first andthird diodes each has an anode and a cathode, means connecting saidfirst diode means anode to said fourth transistor emitter, meansconnecting said third diode anode to said sixth transistor emitter, andmeans connecting the cathodes of said first and third diodes to thebases of said fourth and sixth transistors, said first and secondtransistor means each has a base emitter and collector electrode, meansconnecting the collector of said first transistor to the anode of saidsecond diode, means connecting said first transistor collector to theother terminal of said high voltage source, means connecting said firsttransistor emitter to a source of biasing potential, diode meanscoupling the emitter of said first transistor to the emitter of saidsecond transistor, oscillator means coupled to the bases of said firstand third transistors for alternately rendering them conductive, meansconnecting the collector of said second transistor to the anode of saidfourth diode, means connecting said second transistor collector to theother terminal of said high voltage source, said third and fifthtransistor means each having a collector base and emitter electrode,means connecting the collectors of said third and fifth transistor meansto the cathodes to the respective cathodes of said second and fourthdiodes, means connecting the emitters of said third and fifth transistormeans to said current source, means connecting the base of said thirdtransistor means to the base of said first transistor means and meansconnecting the base of said fifth transistor means to the base of saidsecond transistor means.